Methods for non lot-based integrated circuit manufacturing

ABSTRACT

A method for continuous, non lot-based manufacturing of integrated circuit (IC) devices of the type to each have a unique fuse identification (ID) includes: reading the fuse ID of each of the IC devices; advancing multiple lots of the IC devices through, for example, a test step in the manufacturing process in a substantially continuous manner; generating data, such as test data, related to the advancement of each of the IC devices through the step in the process; and associating the data generated for each of the IC devices with the fuse ID of its associated IC device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/763,104, filed Jun. 14, 2007, now U.S. Pat. No. 7,738,988, issuedJun. 15, 2010, which application is a continuation of U.S. patentapplication Ser. No. 10/205,918, filed Jul. 25, 2002, now U.S. Pat. No.7,555,358, issued Jun. 30, 2009, which is a continuation of U.S. patentapplication Ser. No. 09/137,781, filed Aug. 20, 1998, now U.S. Pat. No.6,427,092, issued Jul. 30, 2002, which is a continuation of U.S. patentapplication Ser. No. 08/822,731, filed Mar. 24, 1997, now U.S. Pat. No.5,856,923, issued Jan. 5, 1999, which is related to the followingapplications: U.S Pat. Ser. No. 08/591,238, filed Jan. 17, 1996, nowabandoned; U.S. Pat. Ser. No. 08/664,109, filed Jun. 13, 1996, now U.S.Pat. No. 5,895,962, issued Apr. 20, 1999; U.S. Pat. Ser. No. 08/785,353,filed Jan. 17, 1997, now U.S. Pat. No. 5,927,512, issued Jul. 27, 1999;U.S. Pat. Ser. No. 08/801,565, filed Feb. 17, 1997, now U.S. Pat. No.5,844,803 issued Dec. 1, 1998; U.S. Pat. Ser. No. 08/806,442, filed Feb.26, 1997, now U.S. Pat. No. 5,915,231, issued Jun. 22, 1999; and U.S.Pat. Ser. No. 08/871,015, filed Jun. 6, 1997, now U.S. Pat. No.5,907,492, issued May 25, 1999. The disclosure of each of the previouslyreferenced U.S. patent applications and patents is hereby incorporatedby reference herein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates in general to integrated circuit (IC)manufacturing and, more specifically, to methods for tracking IC devicesin a substantially continuous flow of IC devices from multiple lotsthrough one or more steps in an IC manufacturing process.

2. State of the Art

Integrated circuits (ICs) are small electronic circuits formed on thesurface of a wafer of semiconductor material, such as silicon, in an ICmanufacturing process referred to as “fabrication.” Once fabricated, ICsare probed to evaluate a variety of their electronic characteristics,cut from the wafer on which they were formed into discrete IC dice or“chips,” and then assembled for customer use using various well-known ICpackaging techniques, including lead frame packaging, Chip-On-Board(COB) packaging, and flip-chip packaging.

During the manufacturing process, ICs generally undergo a variety oftests to ensure they will function properly once shipped. Testingtypically involves a variety of known test steps, such as speed grading,burn-in, and final, which test ICs for defects and functionality andgrade ICs for speed.

ICs are typically tracked through the fabrication, probe, assembly, andtest steps described above so correlations can be found between theresults of tests performed on ICs in the test steps and the “path” theICs took through the manufacturing process. For example, by tracking agroup of ICs through the manufacturing process, it might be determinedthat ICs wire-bonded on a particular wire-bonding machine have anunusually high failure rate when tested. Similarly, it might bedetermined that a test machine itself is failing a disproportionatenumber of ICs. In either case, tracking ICs through the manufacturingprocess allows the source of a problem to be pinpointed and addressed.

As shown in FIG. 1, a conventional procedure 10 for tracking ICs througha process step 12 in an IC manufacturing process involves the use of lotnumbers for the ICs. Lot numbers are first assigned to wafers duringfabrication. Typically, a group of 20-50 wafers receives a single uniquelot number (e.g., 36/1/9970). As the group of wafers proceeds to probe,the wafers are typically split into several sub-lots, with each sub-lotbeing assigned a new lot number (sometimes referred to as a “sub-lot”number) that is a modified form of the group's original lot number(e.g., 36/1/9970/0, 36/1/9970/1, . . . ). As the group continues throughthe manufacturing process, sub-lots are split and re-split for a varietyof reasons until the group is typically split into many sub-lots, allhaving a unique lot number that is a modified form of the group'soriginal lot number.

In the conventional tracking procedure 10, a sub-lot (e.g., sub-lot H)is received from an input queue 14 where sub-lots wait to proceedthrough the process step 12. The process step 12 may be any step in theIC manufacturing process including, for example, probe, wafer saw, speedgrading, burn-in, or final testing.

As a sub-lot advances through the process step 12, data 16 related tothe process step 12 is generated. Such data 16 may include, for example:an identification of the processing equipment and the operatingpersonnel for the process step 12; information regarding the set-up ofthe process step 12; the time and date the sub-lot advanced through theprocess step 12; and yield and test results from the process step 12.

Once a sub-lot has advanced through the process step 12, a processreport 18 is manually or automatically generated based on the generateddata 16. To associate the process report 18, and hence the data 16, withthe ICs in the sub-lot, and thus track the ICs through the process step12, the process report 18 lists the lot number (e.g., “H”) of the ICs inthe sub-lot. Typically, the process report 18 also physicallyaccompanies the sub-lot through the remainder of the manufacturingprocess to ensure that the data 16 is correlated with the ICs in thesub-lot, although this is not necessary if other indicia identifying thelot number of the ICs in the sub-lot physically accompany the sub-lotthrough the manufacturing process.

With the process report 18 generated, a processed sub-lot (e.g., sub-lotH) is cleared from equipment associated with the process step 12 to anoutput queue 20 to prepare the process step 12 for processing anothersub-lot (e.g., sub-lot I). Once the processed sub-lot is cleared, thenext sub-lot can be processed. This “clearing” process is necessarybecause if two sub-lots (e.g., sub-lots H and I) proceed through theprocess step 12 in a continuous manner, the conventional trackingprocedure 10 is unable to correlate the data 16 and the process report18 generated as each of the two sub-lots proceed with the correctsub-lot. Instead, the data 16 for the two sub-lots is mixed, causing theconventional tracking procedure 10 to fail to uniquely track the twosub-lots through the process step 12.

The conventional tracking procedure described above is problematicbecause it makes inefficient use of often very expensive manufacturingand test equipment and other resources by leaving sub-lots “parked” ininput queues while process reports are generated and the equipment iscleared of already processed sub-lots. In process steps that usemultiple machines in parallel to process a sub-lot, some machines may beidle while other machines finish their allotment from the sub-lot beingprocessed and the next sub-lot waits in an input queue. In addition,generation of the process reports, as well as clearing a processedsub-lot from equipment, often requires laborious manual work byoperating personnel. Further, a process report that must physicallyaccompany a sub-lot through the manufacturing process may become lost ordamaged, and thus is not as reliable a means of tracking ICs as isdesired.

As described in U.S. Pat. Nos. 5,301,143, 5,294,812, and 5,103,166, somemethods have been devised to aid quality control personnel in trackingICs undergoing failure analysis back to the wafer from which they come.By tracking the ICs back to their wafer, test data related to the ICscan be correlated to the wafer to pinpoint possible problems with thewafer. Such methods take place “off” the manufacturing line and involvethe use of electrically retrievable identification (ID) codes, such asso-called “fuse IDs,” programmed into individual ICs to identify theICs. Fuse IDs and other electrically retrievable ID codes are typicallyprogrammed into ICs by blowing selected fuses or anti-fuses in circuitryon the ICs so that the circuitry outputs the ID code when accessed.Unfortunately, none of these methods addresses the inefficiency problemscaused by the conventional lot-based tracking procedure described above.

Therefore, there is a need in the art for a procedure for tracking ICsthrough an IC manufacturing process that uses manufacturing resourcesmore efficiently. Such a procedure should not leave equipment idle whileICs wait to be processed. In addition, such a procedure should achieve alevel of reliability not reached by conventional tracking procedures.

BRIEF SUMMARY OF THE INVENTION

An inventive method for tracking IC devices of the type to each have asubstantially unique ID code (e.g., a fuse ID) through a step in an ICmanufacturing process includes: reading the ID code of each of the ICdevices; advancing multiple lots of the IC devices through the step inthe manufacturing process in a substantially continuous manner;generating data, such as processing equipment data or test data, relatedto the advancement of each of the IC devices through the step in theprocess; and associating the data generated for each of the IC deviceswith the ID code of its associated IC device.

By associating the data with the ID codes, the inventive method allowsthe IC devices to be tracked through the step in the process. Further,because multiple lots of the IC devices can advance through the step inthe manufacturing process continuously, manufacturing resources are usedmore efficiently. In addition, because the ID codes and associated dataread and generated using the inventive method need not physicallyaccompany ICs as they progress through the manufacturing process, theinventive method is more reliable than conventional tracking procedures.

In another embodiment, a method of manufacturing IC devices fromsemiconductor wafers includes: providing wafers in multiple lots;fabricating ICs on the wafers; causing each of the ICs to permanentlystore a substantially unique ID code, such as a fuse ID; separating theICs from their wafers to form IC dice; assembling the IC dice into ICdevices; reading the ID code from the IC in each of the IC devices;testing each of the IC devices; while testing the IC devices: advancingthe IC devices from the multiple lots of wafers through at least onetest step in a substantially continuous manner; generating data relatedto the advancement of each of the IC devices through the test step; andassociating the data generated for each of the IC devices with the IDcode of the IC in its associated IC device.

In a further embodiment, a method for correlating variables related toan IC manufacturing process with variables related to the performance ofIC devices as they advance through the process includes: causing each ofmultiple ICs from multiple lots to permanently store a substantiallyunique ID code, such as a fuse ID; reading the ID code from each of theIC devices; advancing the IC devices from the multiple lots through atleast one step in the manufacturing process in a substantiallycontinuous manner; while the IC devices advance through the step in themanufacturing process, generating data related to process variablesassociated with the step in the process; generating data related tovariables associated with the performance of at least some of the ICdevices as they advance through at least one step in the manufacturingprocess; and associating the process variable-related data and theperformance variable-related data generated for each of the IC deviceswith the ID code of the IC device associated with the data to correlatethe process variables with the performance variables.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow diagram showing a process step in a conventionallot-based (IC) manufacturing process; and

FIG. 2 is a flow diagram showing a process step in a substantiallycontinuous, non lot-based IC manufacturing process in accordance withthe present invention.

DETAILED DESCRIPTION OF THE INVENTION

As shown in FIG. 2, an inventive method 30 for tracking IC devicesthrough a step 32 in an IC manufacturing process includes a step 34 ofreceiving IC devices from multiple, mixed input lots 36. It will beunderstood by those having skill in the field of this invention that theinvention is applicable to any IC devices, including Dynamic RandomAccess Memories (DRAMs), Static Random Access Memories (SRAMs),Synchronous DRAMs (SDRAMs), processors, Application Specific ICs(ASICs), Read Only Memory (ROM) ICs, Electrically Erasable ProgrammableROM (EEPROM) ICs, and to mixtures of different types of IC devices.Further, it will be understood that the process step 32 may be any stepin an IC manufacturing process, including assembly and test steps. Itwill also be understood that the process step 32 may encompassprocessing by a single machine, part of a machine, many machinesoperating in series or parallel, or any combination thereof. Inaddition, it will be understood that the step 34 of receiving IC devicesfrom multiple, mixed input lots 36 is without regard to the lots fromwhich the IC devices come, and thus allows a more efficient use ofprocessing equipment than traditional lot-based procedures. It will alsobe understood, of course, that although the present invention isdescribed as being implemented in a single process step 32 for ease ofunderstanding, the invention more typically is implemented on a seriesof process steps, such as all back-end test steps.

The IC devices are each programmed with a unique ID code, such as thewell-known fuse ID described above. Briefly, a fuse ID is programmed inan IC device by selectively blowing fuses or anti-fuses in a circuit onthe IC device so that when the circuit is accessed, it outputs an IDcode. Although it is preferable that the ID code programmed into each ICdevice be unique by specifying, for example, a lot number, wafer number,and wafer position for the IC device, it is not necessary to implementthe present invention. For example, if the ID code is the same for allIC devices derived from the same semiconductor wafer, or from the samelot, it will work for purposes of the present invention.

Before or after the IC devices progress through the process step 32,their ID codes are read and stored in a computer as data 38. As the ICdevices progress through the process step 32, data 40 related to theprocess step 32 is generated for each IC device. Such data 40 mayinclude, for example, process variables such as the processing equipmentused, the operating personnel present, the set-up, and the time and dateof processing for the process step 32, and performance variables such asyield and test results from the process step 32. The set-up for theprocess step 32 may include, for example, a standard set-up or a set-upin accordance with a Special Work Request (SWR) by engineeringpersonnel.

The ID code data 38 and process-related data 40 may be automaticallycorrelated by computer with data from process steps prior to the processstep 32 through reference to the ID codes common to the ID code data 38generated in the process step 32 and ID code data generated in the priorprocess steps. As a result, correlations can be found between processvariables, such as the processing equipment used, and performancevariables, such as test results. Thus, for example, it might bediscerned that the IC devices derived from a particular section of thesemiconductor wafers provided by a particular supplier have an unusuallyhigh failure rate at a particular test step. The process of correlationis preferably performed in real time so information is availableimmediately, although it is within the scope of the present invention toperform the correlation at a later time.

Once the IC devices have advanced through the process step 32, theprocessed IC devices are output from the process step 32 to mixed outputlots 42. It should be understood that, in some cases, the processed ICdevices must be cleared from processing equipment before other ICdevices can be processed, and in other cases, such as in serial-feedmachines, processed IC devices are being output from the process step 32while other IC devices are advancing through the process step 32 andstill other IC devices are being received by the process step 32. Any ofthese cases fall within the scope of the present invention.

It should be understood that by reading the ID codes of processed ICdevices and associating those codes with data generated duringprocessing, the inventive method 30 avoids the need for lot-basedmanufacturing altogether. The mixed input lots 36 and output lots 42 maythen be mixed without regard to lots, and the processing of IC devicesthrough the process step 32 may proceed in a substantially continuousfashion, thus dramatically improving the utilization of processingequipment. In addition, because the ID codes and associated data readand generated using the inventive method need not physically accompanyICs as they progress through the manufacturing process, the inventivemethod is more reliable than conventional tracking procedures.

Although the present invention has been described with reference to aparticular embodiment, the invention is not limited to this describedembodiment. For example, the present invention includes within its scopethe manufacture of Single In-line Memory Modules (SIMMs) and DualIn-line Memory Modules (DIMMs), as well as the IC devices describedabove. Thus, the invention is limited only by the appended claims, whichinclude within their scope all equivalent methods that operate accordingto the principles of the invention as described.

1. A method of tracking a device in a manufacturing process, the methodcomprising: associating a device with a substantially uniqueidentification (ID) code, wherein the substantially unique ID code isretrievable from the device; advancing the device through at least aportion of the manufacturing process with one or more other deviceswithout regard to a lot from which any of the devices comes; generatingdata related to the advancement of the device through the at least aportion of the manufacturing process; associating the data with thesubstantially unique ID code; and outputting the device to a mixedoutput lot comprising devices from one or more lots different from thelot with which the device was associated before advancing through the atleast a portion of the manufacturing process.
 2. The method of claim 1,wherein the substantially unique ID code comprises a fuse ID.
 3. Themethod of claim 1, wherein associating a device with a substantiallyunique ID code comprises programming the device with the substantiallyunique ID code.
 4. The method of claim 1, wherein the at least a portionof the manufacturing process comprises a step in the manufacturingprocess.
 5. The method of claim 1, wherein the device comprises anintegrated circuit (IC) device.
 6. The method of claim 5, wherein thesubstantially unique ID code specifies a lot number, wafer number andwafer position for the IC device.
 7. The method of claim 5, wherein thesubstantially unique ID code is the same for all IC devices derived fromthe same wafer.
 8. The method of claim 5, wherein the substantiallyunique ID code is the same for all IC devices coming from the same lot.9. The method of claim 1, further comprising reading the substantiallyunique ID code before advancing the device through the at least aportion of the manufacturing process.
 10. The method of claim 1, furthercomprising reading the substantially unique ID code after advancing thedevice through the at least a portion of the manufacturing process. 11.The method of claim 1, further comprising storing the substantiallyunique ID code before advancing the device through the at least aportion of the manufacturing process.
 12. The method of claim 1, furthercomprising storing the substantially unique ID code after advancing thedevice through the at least a portion of the manufacturing process. 13.The method of claim 1, wherein the data comprises process-related data.14. The method of claim 1, wherein the data comprises a processvariable.
 15. The method of claim 14, wherein the data comprises aperformance variable.
 16. The method of claim 15, further comprisingdetermining whether a correlation exists between the process variableand the performance variable.
 17. The method of claim 1, wherein thedata comprises a performance variable.
 18. A method of tracking a devicein a manufacturing process, the method comprising: associating a devicewith a substantially unique identification (ID) code, wherein thesubstantially unique ID code is retrievable from the device; mixing thedevice with other devices without regard to lots; advancing the devicewith the other devices through at least a portion of the manufacturingprocess without regard to a lot from which the device comes; generatingdata related to the advancement of the device through the at least aportion of the manufacturing process; associating the data with thesubstantially unique ID code; and outputting the device to a mixedoutput lot comprising devices from one or more lots different from thelot with which the device was associated before advancing through the atleast a portion of the manufacturing process.
 19. A method of tracking adevice in a manufacturing process, the method comprising: receiving thedevice from a plurality of mixed lots of devices without regard to a lotof the plurality of mixed lots of devices from which the device comes;associating the device with a substantially unique identification (ID)code, wherein the substantially unique ID code is retrievable from thedevice; advancing the device through at least a portion of themanufacturing process without regard to the lot of the plurality ofmixed lots of devices from which the device comes; generating datarelated to the advancement of the device through the at least a portionof the manufacturing process; associating the data with thesubstantially unique ID code; and outputting the device to a mixedoutput lot comprising devices from one or more lots different from thelot with which the device was associated before advancing through the atleast a portion of the manufacturing process.